TKT and neoplasm: Tumor suppressor protein p53 is a transcription factor that regulates the expression of many genes that are crucial in mediating its tumor suppressing activity.20, 21 Therefore, we checked a dose-dependent effect of NP on p21 transcription which is under a direct control of p53 transcriptional activity.33 A549 cells were transiently co-transfected with p21 luciferase reporter plasmid containing the p53 binding site on its promoter together with indicated concentrations of pEGFP-NP and pcDNA-p53 and a control plasmid, Renilla luciferase pRL-TK.